Attachment of moving blades of elastic-fluid turbines



H. L. GUY.

ATTACHMENT 0F MOVING BLADES 0F ELASTIC FLUID TURBINES.

APPLICATION FILED JAN. 31, 1917.

1,347,031, Patented July 20,1920.

D J J Q .w ITN E55 ES I INVENTOR M a il y UNITED STATES PATENT OFFICE. I

HENRY LEWIS GUY, OF MANCHESTER, ENGLAND, ASSIGNOR TO THE BRITISH WEST-INGHOUSE ELECTRIC AND MANUFACTURING COMPANY LIMITED, A COMPANY OF GREATBRITAIN.

ATTACHMENT 0F MOVING BLADES 0F ELASTIC-FLUID TURBINES.

Specification of Letters Patent.

Patented July 20, 1920.

Application filed January 31, 1917. Serial No. 145,630.

To all whom it may concern:

Be it known that I, HENRY LEWIS GUY, a subject of the King of GreatBritain, and a resident of Manchester, in the county of Lancaster,England, have invented a new and useful Improvement Relating to theAttachments of Moving Blades of Elastic- Fluid Turbines, of which thefollowing is a specification.

This invention has for its object to provide an improved attachment forthe moving blades of an elastic fluid turbine of the kind in which theturbine wheel, to which the blades are to be attached, is slotted in anaxial direction one slot being provided for the reception of each bladeand the blades are furnished with tongues, shaped to fit the axial slotsin the wheel, each blade being secured in its slot by two or more rivetsor pins located in different pitch circles the holes for the receptionof said pins being drilled or formed in an axial direction in such amanner that one half of each pin lies in the side of the slot in thewheel and the other half in the tongue of the blade.

The invention has for its object to provide an improved blade attachmentof the above kind which with a similar amount of material will withstandgreater operating stresses as rivets or pins of larger diameter can beused to secure the blades in position than with the attachment ashitherto constructed.

According to this invention the slots in the turbine wheel are taperedthe greatest width of the slots in a circumferential direction being attheir outer ends. The tongues of the blades are tapered to correspondwith the slots and are secured in position therein by rivets or pins inthe manner above described.

The improved attachment is illustrated in the accompanying drawing inwhich 3 is a fragment of a turbine wheel having axial tapered slots 4,4, in its periphery, one slot being provided for each blade. The blades5 are provided at the root with tongues 6 tapered to fit the slots 4.Two series of holes on different pitch circles are drilled in an axialdirection in such a manner that one half of each securing pin or rivet 7lies in the side of a slot 4 and the other half of said pin or rivet inthe tongue 6 of the blade in said slot as shown.

lVhere two securing pins of equal diameter are used, the circumferentialthickness of the tongue 6 at the outer pin 7 should preferably be twicethe thickness of the tongue at the inner pin 7. If three pins are usedthe thickness of the tongue at the middle pin should be twice thethickness of the tongue at the pin nearest the wheel axis while thethickness of the tongue 6 at the outermost pin 7 should be three timesthat of the tongue at the innermost pin. If, however, pins of unequaldiameter are used the ratio of the circumferential thicknesses of thetongue at the places adjacent to the pins should be equal to the sum ofthe diameters of the two pins divided by the diameter of the pin nearestthe wheel axis.

The prime object of this invention is to provide a fastening means for aturbine blade which will result in a reduction in the weight of therevolving mass at or near the periphery of the revolving wheels in theturbine. My fastening means is designed to secure the maximum strengthper unit weight of the material employed. In a blade fastening of thisnature there are two principal stresses to be taken into account, onethe shearing stress of the rivets and the other a tensile stress of theblade shank or of the projecting tooth of the wheel at or near where therivets connect these two parts. The present blade fastening has whatmight be termed five danger points, namely, the shearing stresses in thetwo rivets and the tensile or tearing stresses of the blade shank and ofthe wheel across the narrowest portion, that is opposite the groovesformed for the reception of the rivets. Taking into consideration thematerials employed and the relative resistances to the shearing andtensile stresses, the blade fastening is so calculated that all of thesestresses are sub stantially equal and therefore the factor of safety ofthe blade fastening is substantially equal at all. these five differentpoints.

The rivets or pins may be secured in position in any suitable way.

I claim as my invention:

1. In combination with a turbine rotor provided with an axiallyextending tapered slot having its greatest circumferential width at itsouter end, a blade having a tongue tapered to correspond with said slot,and two securing pins for the blade passing half through said tongue andhalf through the walls of said slot and located in difierent pitchcircles.

2. In combination with a turbine rotor provided with an axiallyextending tapered slot having its greatest circumferential width at itsouter end, a blade having a tongue tapered to correspond with said slot,and two securing pins for the blade located on opposite sides of saidtongue passing half through said tongue and half through the walls ofsaid slot and located in different pitch circles.

3. In combination with a turbine rotor provided with axially extendingtapered slots having their greatest circumferential widths at theirouter ends, a blade for each slot having a tongue tapered to correspondwith its slot, and two securing pins for each blade located on oppositesides of said tongue and passing half through said tongue and halfthrough the adjacent wall of said slots and located in different pitchcircles.

4. In combination with a turbine rotor provided with an axiallyextending tapered slot having its greatest circumferential width at itsouter end, one wall of said slot extending radially of the rotor whilethe other ary, 1917.

HENRY LEWIS GUY. Witnesses:

F. NIXON, W. MORRIS.

